A general body cavity medical probe may be inserted into the patient's body cavity for either measuring vital signs or for providing treatment. There are numerous type of general body cavity probes, such as a medical ear thermometer. General body cavity probes may contain a functional module to perform the intended medical measurement or procedure. For a medical ear thermometer, the functional module may be an infrared (“IR”) temperature sensor.
Temperature of an object, specifically of a living being such as a human or an animal, can be measured by thermal conduction or thermal radiation. For thermal conduction, a temperature sensing probe is brought into a physical contact with a surface of the living being. For thermal radiation, a temperature sensing probe is brought near the surface of a the living being and aimed at the area of interest, such as within the open space of a body cavity. Naturally emanated electromagnetic radiation in the mid and far infrared spectral ranges is detected by an appropriate sensor, whose output signal indicates the surface temperature of an object. For both thermal conduction and thermal radiation measurement methods, the temperature sensor is positioned inside or coupled to the medical probe.
Medical thermometers that operate by contact, for example, oral or rectal, may use a probe cover, for instance a sanitary probe cover. Thermal energy (i.e., heat) is transmitted through the probe cover by thermal conduction, thus at least the portion of the probe cover material overlying the thermal sensor should be highly transmissive of thermal energy. Various conventional probe covers for contact thermometers are described in, for example, in U.S. Pat. No. 4,159,766 issued to Kluge, which is hereby incorporated by reference in its entirety.
Medical thermometers that operate by radiation may also use a probe cover, because the possibility still exists of contact with the body of the patient. For example, when measuring the temperature of a tympanic membrane and the surrounding tissue inside the ear canal, the probe is inserted into the ear canal body cavity and may contact the wall of the ear canal. Before insertion, a probe cover may be installed onto the probe to envelop its parts that otherwise might come in contact with the patient's skin. Such a cover provides sanitary protection against contamination of the probe by ear wax and other soiling biological compounds, and includes properties that promote accurate temperature measurement by the detection of infrared signal. Such properties include a good transparency of the front portion of the probe cover in at least the spectral range of interest, low directional distortion of optical rays, tight manufacturing tolerances, stability of the optical properties during installation onto the probe, long term storage stability, etc. Probe covers for the IR thermometers are exemplified by U.S. Pat. No. 5,088,834 issued to Howe et al. and U.S. Pat. No. 5,163,418 issued to Fraden et al., both of which are hereby incorporated by reference in their entirety.
A probe cover may include one or more components such as polyethylene, polypropylene, and copolymers thereof. Probe cover materials may also possess relatively low absorption of electromagnetic energy over a broad spectral range from visible to the far infrared.
FIG. 1 is an example of a medical device having a probe intended for insertion into a body cavity, illustrating a perspective view of the infrared ear thermometer Model “Braun 4000” produced by Kaz, Inc., as known in the art. The example of FIG. 1 includes a thermometer body 1 having a display 2, a power button 3, a probe 7, a probe cover sensing switch 8, and a probe cover ejecting ring 5. Before measuring temperature, a reusable or disposable probe cover 6 is moved in a direction 12 to be positioned over probe 7. The probe cover has a skirt 9 and a groove 10. When installed onto probe 7, groove 10 engages with the offset 11 that is part of the probe 7. This coupling will hold the probe cover 6 on the probe 7 during use. Skirt 9 actuates switch 8 to generate a signal going to the internal electronic circuit indicating a correct installation of the probe cover. If no probe cover is detected by the switch 8, the internal circuit may either warn the operator or make the thermometer inoperable to prevent an erroneous reading.
When a medical probe is used, either with or without a probe cover, it may be desirable to detect either a close proximity of the probe to the patient body surface, or to detect insertion of the probe into a body cavity, such as an ear canal. A shortcoming of the known art is that no medical thermometer has a capability of detecting the probe position relative to the ear canal. Therefore, a need exists to provide such a proximity measurement.